a) Field of the Invention
The present invention relates to a magnetoresistive effect type thin film magneto-electric transducer (hereinafter called "MR type magnetic head element") which is used as a reproduction head element for magnetic recording media such as hard disks.
b) Description of the Related Art
An MR type magnetic head element is dedicated to reproduction only which reproduces information recorded on a magnetic recording medium by detecting a magnetic field from magnetic poles in the medium with a magnetoresistive type MR head element. As compared to induction type magnetic head elements, MR effect type magnetic head elements can improve track density and linear recording density. A reproducing MR type magnetic head element is used in combination with a recording induction type magnetic head element to constitute an induction-MR type composite magnetic head for magnetic disks such as hard disks.
A magnetic sensor film (MR element) of a conventional MR type magnetic head element has generally a of straight line shape as viewed from the pole top face. An MR type magnetic head element, the magnetic sensor film of which has a trapezoidal shape as viewed from the pole top face, has been proposed in JP-A 8-185612 and JP-A 8-185613 assigned to the present applicant. FIG. 2 shows the main structure of such an MR type magnetic head element 28. The pole top face TF is directed toward recording media. A lead 16 is formed on an unrepresented lower gap layer, the lead 16 being a lamination of a magnetic film 10, an electrically conductive film 12, and a magnetic film 14. A trapezoidal groove 18 is formed in this lead 16 which is divided into right and left portions 16a and 16b. A magnetic sensor film 26 is disposed over the right and left leads 16b and 16a and groove 18, the sensor film 26 being a lamination of an MR film 20, a spacer 22 and a soft adjacent layer (SAL) bias film 24. An active region 26a of this trapezoidal magnetic sensor film 26 is defined between the inner lower sharp edges of the right and left leads 16b and 16a (at the bottom area of the groove 18). This active region 26a detects signals recorded on each track of a magnetic recording medium (magnetic disk). The width TH1 of the active region 26a corresponds to a track width. However, slanted regions 26b and 26c of the magnetic sensor film 26, formed on slanted surfaces of the trapezoidal groove 18 at the right and left sides of the active region 26a, have lower reproduction sensitivities because these regions have azimuth angles relative to signals recorded on each track. Therefore, even if a track shifts right or left from the active region 26a, the slanted regions 26b and 26c affect less the magnetization of the active regions 26a, improving the symmetry of off-track characteristics relative to the center of the track and also reducing side lobes. The side lobe is a small bump which is generated in the off-track characteristics asymmetrically with respect to the center. Since the off-track characteristics becomes approximately symmetrical with respect to the center, a tracking servo to locate the magnetic head over a desired track even if it is narrow and high density recording and reproduction become possible. Furthermore, crosstalk between adjacent tracks can be reduced. Still further, since side lobes can be reduced without increasing uniaxial anisotropic bias magnetic fields, reproduction sensitivity can be prevented from being lowered.
The trapezoidal magnetic sensor film 20 of such an MR type magnetic head element 28 is bent at transition regions 30 from the bottom to slanted surfaces of the trapezoidal shape. Therefore, these transition regions 30 of the MR film 20 are likely to become multi-axial because of the magnetic anisotropy effects, and Barkhausen noises are easy to generate because of a change in magnetic domains. This phenomenon becomes more conspicuous the larger the aspect ratio of the length of the magnetic sensor film 26 in the depth direction (element height TH2) to the track width TH1 and the smaller the gap thickness between the upper and lower shield layers (not shown) sandwiching the magnetic sensor film 26.